Ski touring skis are lighter than alpine skis and are provided with bindings that make it possible to release the heel to facilitate uphill climb movements and to lock it to go downhill.
In general, ski boots must comply with standards that vary depending on the individual skiing disciplines and in each discipline they are interconnected to the skis through coupling systems that are such as to allow the skier's energy pulse to be transferred rapidly and precisely to the skis.
In particular, ski touring boots suitable for going downhill have a shaped sole whose profile is complementary to a shim provided on the surface of the binding. Said elements constitute a constraint for purely lateral or longitudinal movements, while they can slide with respect to each other when they are subjected to a voluntary relative twist movement around the heel of the boot, thus eliminating the constraint existing between the boot and the binding. The underside of the sole is smooth and rigid, in such a way as to minimize friction between the ski and the boot when it is necessary to separate said elements quickly.
Instead, the ski touring boots suitable for going uphill typically have a tank sole in rubber or composite material, so as to increase friction between the sole and the ground and make it easier and safer to walk on the snow.
Among the different types of standard bindings used, the DYNAFIT® ski bindings standard is widespread, in which the binding is carried out by means of pins that are oriented crosswise and integral with the ski, and fit into recesses having a cylindrical profile, successively indicated as bushings, and provided laterally on the front of the boot. This type of binding localizes the operating point of the constraint, and therefore the point of transfer of the energy pulses exerted by the skier, on the connection between the pins of the binding and the bushings of the boot.
A first type of boots belonging to the known art and used for ski touring when going uphill includes a tank sole fixedly constrained to the hull of the boot. As shown in FIG. 1, on the front of the sole, in lateral position, the boot is provided with bushings that serve as seats for the pins of the DYNAFIT® ski binding. Ski boots with fixed sole have the disadvantage that they can be used for ski touring only when going uphill and not when going downhill.
In order to overcome said drawback, the patent WO 2009/003904 A1 discloses a boot that makes it possible to mount different sets of soles on the same hull, each set being in compliance with the standards that rule the different skiing disciplines, for example alpine skiing and ski touring. Each set of soles is made up of a front element and a back element that are separated from each other and removably fixed to plates that are fixedly constrained to the hull of the boot by means of fixing screws. In this way it is possible to use a single hull for different applications, according to the type of sole integrated therein. If a boot is improved for ski touring used for going uphill, the front element of the removable sole will be provided with the bushings, located laterally, that allow the boot to be constrained to the ski using the corresponding DYNAFIT® ski binding.
FIGS. 2 and 3 respectively illustrate ski touring boots used for going uphill and downhill, carried out according to the technical solution described above.
FIG. 4 shows the front element of the ski touring boot according to the known art and the front elements of the soles in compliance with the standards in force and used for going uphill and downhill, respectively.
The boot carried out according to the solution illustrated in FIG. 4 has the disadvantage of reducing the skier's control precision and rapidity when going uphill compared to the boot with fixed sole. The constraint system between the sole and the fixed plate of the hull, consisting of fixing screws, in fact can introduce a play between the two elements, due to misalignments and lack of homogeneity in size between the fixing screws and the corresponding seats provided in the removable sole and in the hull's plate. Said interconnection faults between the removable sole and the fixed plate can be generated during the sporting activity or already during assembly.
As the bushings of the boot are located on the removable sole, any play between the sole and the fixed plate of the hull involves a play between the ski and the boot, which limits the precision and rapidity with which the skier can transfer an energy pulse to the skis, with consequent reduced control and therefore less safety for the skier.